22,432 research outputs found
Orbital selective and tunable Kondo effect of magnetic adatoms on graphene: Correlated electronic structure calculations
We have studied the effect of dynamical correlations on the electronic
structure of single Co adatoms on graphene monolayers with a recently developed
novel method for nanoscopic materials that combines density functional
calculations with a fully dynamical treatment of the strongly interacting
3d-electrons. The coupling of the Co 3d-shell to the graphene substrate and
hence the dynamic correlations are strongly dependent on the orbital symmetry
and the system parameters (temperature, distance of the adatom from the
graphene sheet, gate voltage). When the Kondo effect takes place, we find that
the dynamical correlations give rise to strongly temperature-dependent peaks in
the Co 3d-spectra near the Fermi level. Moreover, we find that the Kondo effect
can be tuned by the application of a gate voltage. It turns out that the
position of the Kondo peaks is pinned to the Dirac points of graphene rather
than to the chemical potential.Comment: 12 pages, 7 figure
A probabilistic approach to reduce the route establishment overhead in AODV algorithm for manet
Mobile Ad-hoc Networks (MANETS) is a collection of wireless nodes without any
infrastructure support. The nodes in MANET can act as either router or source
and the control of the network is distributed among nodes. The nodes in MANETS
are highly mobile and it maintains dynamic interconnection between those mobile
nodes. MANTEs have been considered as isolated stand-alone network. This can
turn the dream of networking "at any time and at any where" into reality. The
main purpose of this paper is to study the issues in route discovery process in
AODV protocol for MANET. Flooding of route request message imposes major
concern in route establishment. This paper suggests a new approach to reduce
the routing overhead during the route discovery phase. By considering the
previous behaviour of the network, the new protocol reduces the unwanted
searches during route establishment processComment: International Journal of Distributed and Parallel Systems (IJDPS)
Vol.3, No.2, March 201
1D to 3D Crossover of a Spin-Imbalanced Fermi Gas
We have characterized the one-dimensional (1D) to three-dimensional (3D)
crossover of a two-component spin-imbalanced Fermi gas of 6-lithium atoms in a
2D optical lattice by varying the lattice tunneling and the interactions. The
gas phase separates, and we detect the phase boundaries using in situ imaging
of the inhomogeneous density profiles. The locations of the phases are inverted
in 1D as compared to 3D, thus providing a clear signature of the crossover. By
scaling the tunneling rate with respect to the pair binding energy, we observe
a collapse of the data to a universal crossover point at a scaled tunneling
value of 0.025(7).Comment: 5 pages, 4 figure
The Discrete Fundamental Group of the Associahedron, and the Exchange Module
The associahedron is an object that has been well studied and has numerous
applications, particularly in the theory of operads, the study of non-crossing
partitions, lattice theory and more recently in the study of cluster algebras.
We approach the associahedron from the point of view of discrete homotopy
theory. We study the abelianization of the discrete fundamental group, and show
that it is free abelian of rank . We also find a combinatorial
description for a basis of this rank. We also introduce the exchange module of
the type cluster algebra, used to model the relations in the cluster
algebra. We use the discrete fundamental group to the study of exchange module,
and show that it is also free abelian of rank .Comment: 16 pages, 4 figure
New path description for the M(k+1,2k+3) models and the dual Z_k graded parafermions
We present a new path description for the states of the non-unitary
M(k+1,2k+3) models. This description differs from the one induced by the
Forrester-Baxter solution, in terms of configuration sums, of their
restricted-solid-on-solid model. The proposed path representation is actually
very similar to the one underlying the unitary minimal models M(k+1,k+2), with
an analogous Fermi-gas interpretation. This interpretation leads to fermionic
expressions for the finitized M(k+1,2k+3) characters, whose infinite-length
limit represent new fermionic characters for the irreducible modules. The
M(k+1,2k+3) models are also shown to be related to the Z_k graded parafermions
via a (q to 1/q) duality transformation.Comment: 43 pages (minor typo corrected and minor rewording in the
introduction
A mathematical model of tumor self-seeding reveals secondary metastatic deposits as drivers of primary tumor growth
Two models of circulating tumor cell (CTC) dynamics have been proposed to
explain the phenomenon of tumor 'self-seeding', whereby CTCs repopulate the
primary tumor and accelerate growth: Primary Seeding, where cells from a
primary tumor shed into the vasculature and return back to the primary
themselves; and Secondary Seeding, where cells from the primary first
metastasize in a secondary tissue and form microscopic secondary deposits,
which then shed cells into the vasculature returning to the primary. These two
models are difficult to distinguish experimentally, yet the differences between
them is of great importance to both our understanding of the metastatic process
and also for designing methods of intervention. Therefore we developed a
mathematical model to test the relative likelihood of these two phenomena in
the subset of tumours whose shed CTCs first encounter the lung capillary bed,
and show that Secondary Seeding is several orders of magnitude more likely than
Primary seeding. We suggest how this difference could affect tumour evolution,
progression and therapy, and propose several possible methods of experimental
validation.Comment: 20 pages, 4 figure
SM(2,4k) fermionic characters and restricted jagged partitions
A derivation of the basis of states for the superconformal minimal
models is presented. It relies on a general hypothesis concerning the role of
the null field of dimension . The basis is expressed solely in terms of
modes and it takes the form of simple exclusion conditions (being thus a
quasi-particle-type basis). Its elements are in correspondence with
-restricted jagged partitions. The generating functions of the latter
provide novel fermionic forms for the characters of the irreducible
representations in both Ramond and Neveu-Schwarz sectors.Comment: 12 page
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